You have one cow and one anti-cow. They collide. You now have no cows and a very large crater.

Antimatter 2

You have one cow and one anti-cow. They collide. You don't have cows. Or planet.

Astronomy

You have two cows. Due to size differences among bovines, they're renamed to a calf or "dwarf cow". Even though they're similar in size, since one is smaller, it's not considered a "cow" at all, but instead must be referred to as a "natural satellite of a dwarf cow."

You have two cows, both of which are compressed into one minuscule ball, along with all the other cows in the universe. In less than a fraction of a second, this ball explodes. Boiling cow guts traveling at close to light speed collide with your face. It is vaporized.

Big Bang 2

You have no cows. Which explode. Now you have 2 cows.

Binary

You have 10 cows.

Binomial nomenclature

You have two bos tauri

Biology

You have two members of the species bos tauri, one male (XY) and one female (XX). Through meiosis and sexual reproduction, they produce more cows, and after many generations evolve into a bovine freak of nature through genetic drift, mutation, natural selection, and inbreeding.

Bioengineering

You have two cows. You gut them and fill their empty bodies with specially prepared genetic material. They now cure cancer.

You have two D-Block transition metal cowions. You pour water over one of them and it sticks to the cowion, causing it to produce strawberry flavoured milk. Dousing the other with concentrated aqueous ammonia results in it producing banana flavoured milk. You deduce that your cowions are chromium, in two plus oxidation state.

Classical Mechanics

You have two cows. They produce milk. In 300 years, someone will develop a theory that will eventually make you question the very existence of cows entirely.

Computer Science

You have n cows. You mathematically determine that it'll take no less than years to produce k quarts of milk. You spend your free time building a bigger farm in the hopes of speeding up the process.

Dark Matter

You have two cows. Every morning when you milk your cows you get four times as much milk as you predicted. You posit your owning of at least six more cows, completely invisible, that keep screwing up your milking calculations.

Digital Electronics

Cows = Cow1 AND Cow2. Now, find the truth-table.

Dimensional Analysis

1 Farmer = 2 Cows. Therefore, 42.91 Farmers = 85.82 Cows.

Electronic engineering

You have 3 dB cows.

Entropy

You have two cows. Unless you work hard and milk them, they'll make a big mess and randomly kill each other.

Evolution

You want two cows? Just get some micro-algae - and wait.

Evolution (2)

You have proof of two cows. Many people reject this evidence because they say that the two cows are a hoax. When asked for proof that the two cows don't exist, they give none and complain that the people who believe that the two cows DO exist don't have any evidence and that they are going to their imaginary pain world. They also say that a giant omnipotent cow created them, and their proof is a small book. People ask what makes the book true, and they answer that it was written in the same book that it was true.

Flash ActionScript 2.0

onClipEvent(cow){
_root.cowtext = "You now have two cows"
createCows()
}

Fusion (general)

You have two cows. They need to collide with each other at high speeds to fuse to form a supercow. Unfortunately, cattle don't like being that close together. Thankfully, nobody really knows exactly where a given cow is, so if they're running fast enough, they might already have collided. Unfortunately, in a given pasture, most of the cows will be going far slower than the fastest ones. You think you have a good idea on how to make them all run fast. Todd Rider dashes your dreams.

Fusion (cold)

You have two cows embedded in a block of platinum. You give them a little bit of grass, and, voila -- a supercow! You try to replicate what happened with two other cows. You fail and end up spending the rest of your life trying to fuse two more cows together. Other scientists either ignore you or question whether you already had a supercow in your experimental apparatus.

Fusion (moo-on catalyzed)

You have two cows and a chicken. Firing the chicken at the cows makes them merge into a supercow, but unfortunately the chicken tends to get stuck to the supercow, preventing it from joining together too many other cows before it dies of asphyxiation.

Fusion (sonofusion)

You have two aqueous cows. You play heavy metal for them, and they mosh so hard that they join together. Someone sees the cows and suggests that you simply duct-taped them together. Random people manage to confirm heavy-metal-cow joining, while others keep suggesting evidence for duct tape marks.

Fusion (magnetic)

You have two cows. You do the Brillouin limit calculation, and decide you'll have better luck just setting them free.

Fusion (inertial electrostatic)

You have two cows, floating around in a vacuum. You rub them with a sheep to give them a static charge, then place the sheep near the center to attract them. Hopefully, one of these days, the cattle will hit each other and form a supercow. Hopefully they won't hit the sheep first. Popular among amateur farmers!

Fusion (polywell)

You have two cows in a vacuum, statically charged by sheep like above. You throw the sheep around in the hope that moving sheep are harder to hit.

Fusion (inertial)

You have two cows inside a cow ball. You build a laser system the size of a football stadium that can briefly produce sun-dwarfing energies in order to compress the cow ball and make a supercow. It will lead to new weapons! Free energy! We just need a little bit more funding because you see, our budget estimate was off by an order of magnitude. But think -- new weapons, free energy!

Fusion (tokamak)

You have twenty million cows. The problem with prior attempts to make supercows is that people just weren't thinking big enough. Bigger is better. The experimental cattle reactor's price tag is best written in exponential notation.

Genetics

You have a cow and a bull. They reproduce, and the sperm combines with the egg to create a baby cow with traits of the bull and cow. You then have a cow, a bull and a calf. No one cares, because this happens every freaking day.

Heisenberg Uncertainty Principle

You know you have exactly two cows, and, based upon complex mathematical stuff that no one understands or gives a rip about, you can infer the locations where the cows are most likely to be.

Heisenberg Uncertainty Principle 2

You know exactly where your two cows are. You have no idea where they've been, or where they're going. You party until they come home.

Heisenberg Uncertainty Principle 3

You have two cows. You know exactly how fast they are moving. Even though they are moving extremely slowly, you have no idea where they are.

Heisenberg Uncertainty Principle 4

You cannot truly know the location and the speed of your two cows at the same time; you can only know the speed OR the location. Using this fact, some idiot figures out that no-one can have no cows and that cows apear and disapear from existence all the time. You have two cows. Now you have four cows. Now you have no cows. Now you have six cows, two anti-cows, three sheep and a catgirl.

International Space Development Conference

You have methane detected on Mars, and want to know its source. Positing a bovine-source theory, one scientist proposes a scout program probe that could detect the methane from two cows on the planet. [1]

Irresistible Force Paradox

You have two cows. The first stands completely still and cannot be moved. The second moves so fast, it becomes an irresistible force. They collide. The result makes your head explode.

l'Hôpital

You have n cows, and n infinitely approaches 2. You divide your cows by a function where . You then take the derivative of both the top and the bottom of the fraction and discover that you have 2 cows. Then you debate for hours over whether there should be an "s" in l'Hôpital.

Laplace Transform

You have two cows. You convolute them and integrate them from the barnyard to infinity. Now you have one very ugly cow.

Mathematics

You have 2cos.

Mathematical

You have 2 cows, you kill three cows, now you have one negative cow.

Mathematics 2

You have two cows. You can put your two cows in either order and get the same result because they are commootative.

Mathematics 3

Mathematics 4

Paradox

You have two cows. One goes back in time and stops their mother from getting pregnant with them. You have no cows. The cows are never born so one never goes back in time to stop his mother from giving birth. You have 2 cows. One goes back in time and...

Paradox (2)

You have two cows, each one taller than the other.

Paradox (3)

You have no cows, both of which die because of starvation.

Particle Physics

You have two groups of 1011 cows. You collide them together and detect the elephants created at the vertices.

Physics

You have two cows (each 180kg), one running in a negative direction toward the other at -20 meters/second. It hits in an inelastic collision, causing a conversion of kinetic energy into heat. You get a janitor to clean up the mess.

Physics (2)

You have two spherical cows.

Prehistory

Paleolithic You have two aurochs. You kill one with a spear. The other gores you to death.

Neolithic You have two aurochs. You kill one with a spear. You attempt to tame the other.

Quantum Entanglement

You have two cows; one is black, the other is brown. You see the black one - you assess that the other one, which you cannot see, is brown. You are baffled by your own ability to make this judgment.

Quantum Entanglement (2)

You have two cows. You kill one. The other one dies at exactly the same time, in exactly the same way.

Quantum Theory

You have an infinite number of cows until you observe them. Once you do, you have two cows.

Quantum Theory 2

You probably have two cows. On rare occasions you have zero, on other occasions you have infinite. But most of the time, you have two.

Quantum Mechanics

You have two cows that technically aren't cows but a cow/sheep duality.

Relativity

You have two cows. If you shoot one of the cows into orbit at close to light speed, when it gets back to Earth it will be dead, because cows can't operate spacecraft.

Remote sensing

You have two cows. You image them at different distances to determine the angular resolution of your sensor.

Schrödinger's Cows

You have two cows. They are both alive and dead in a large metal box.

Schrödinger's Cows 2

You have two cows. You seal them in a metal crate with a death button inside. You then create a theory explaining how the cows are both alive and dead. You then go party with your buddies, leaving the crate behind. A week later, you remember that you forgot to let the cows out of the crate. So you get another beer and assume they died, totally ruining your theory in the process.

Scientific Discipline Rivalry (1)

You have two cows. You ask a mathematician, a physicist, and an engineer to come up with the volume of the two cows.

The mathematician calculates the value of 2( Acow · Hcow · μ )

The physicist uses relative displacement to determine the volume of the cows.

And the engineer looks up volume of two cows in his cow manual.

Scientific Discipline Rivalry (2)

An engineer, a physicist and a mathematician see two cows. A joke ensues that makes engineers, physicists and mathematicians laugh at themselves.

Scientific Notation

You have 2*100 cows

Scientific Research

You find that there are two cows, but the people who fund your research don't want it to be that way. You lose funding and get a proper job.

You have two cows, but you don't know why. You think of a violin and decide to create an entire model of fundamental physics around it. You add dimensions and random nonsense that no one can prove or disprove to your theory. You keep doing this and hope it will tell you where your cows came from.

String Theory 2

You have 24 cows, at least. They are all rolled up into very tiny strings - except for two of them.

You have a 3-manifold homeomorphic to the direct sum of two cows. We can consider a map from one cow to the other; this map induces an automorphism of the Homoology groups of Cow. You spend three days trying to decide whether these cows are contractible, and, if so, whether they'll still give milk.

Thermite

You have one cow, but it can react with the power of a whole herd of cows located in the groups below it.

Vaccination

You have two cows. One of them used to have trace amounts of mercury 30 years ago, but no longer does. However, many stupid single mothers attempting to raise boys by themselves insist that your other cow - the one that does not and never did contain mercury - is making their sons behave weirdly: becoming interested in science and math instead of wanting to gossip with their many friends on the phone for hours like a normal person does. You explain this to them, but they say if it wasn't the mercury, then it's something else.